Question

Find the surface area of the sphere with the given dimension. Leave your answer in terms of .
18.
radius of 70 m (1 point)

4,900 m2
19,600 m2
9,800 m2
14,700 m2

Answer 1

Do you know the formula for the surface area of a sphere?

Answer 2

no

Answer 3

i think its B will explain it tho step by step

Answer 4

You should memorize it. It's

\[A=4 \pi r^2\] where r is the radius, of course.

Answer 5

i got 61544 buts its not an answer choice

Answer 6

Remember that it asked you to leave the answer in terms of pi, which means that you don't multiply an approximation of pi, so your answer should look like _____*pi.

Answer 7

uhhh yeah idk how to do any of this

Answer 8

Look at the formula:
A = 4 * pi * r^2
You have the fact that r=70, so plug it in.
A = 4 * pi * 70^2
A = 4 * pi * 4900
You want your answer to look like A = _____*pi m^2.

Answer 9

so its 4900

Answer 10

9.
A spherical balloon has a circumference of 21 cm. What is the approximate surface area of the balloon to the nearest square centimeter? (1 point)

1,385 cm2
561 cm2
346 cm2
140 cm2

Answer 11

Not quite.
A = 4 * pi * 4900
It needs to simplify so that there's only one string of numbers, with pi after it.

Answer 12

im lost i really dont get this so its not 4900

Answer 13

It's not 4900. Look at what you have:
A = 4 * pi * 4900
If you reorder it, that's
A = 4 * 4900 * pi
You can simplify it so that it's in "terms of pi" from here. Remember that it should look like:
A = ____ * pi

Answer 14

so its 4900* pi?

Answer 15

No, you're still missing something.
A = 4*4900 * pi

Answer 16

i got 19,600 ?

Answer 17

Yes! 19600pi m^2 is the answer.

Answer 18

thanks

Answer 19

As for your second question, let's look at what we have:
C = 21 cm
A = 4*pi*r^2
We can't plug the circumference into this formula, though. You have to find the radius now, from the circumference formula:
C = 2*pi*r
That means:
21 = 2*pi*r
Now we need to solve for the radius, r.

Answer 20

how to find the radius

Answer 21

You have
21=2*pi*r
Use algebra to isolate r.

Answer 22

im so confused will u pls explain.... i am dyslexic

Answer 23

21 = 2 * pi * r
Remember that in algebra, we do the opposite function to the opposite function to move things to the other side. This is "isolating the variable."
For example, when on one side we're multiplying, we can divide both sides to move it to the other side.

21 = 2 * pi * r
To get rid of the 2 we're multiplying on the right, we divide both sides by 2, and we get:
21/2 = 2/2 * pi * r
This simplifies down to:
10.5 = pi * r
To get rid of the pi we're multiplying on the right, we divide both sides by pi, and we get:
10.5/pi = pi/pi * r
This simplifies down to:
3.342 = r
r = 3.342
That's the radius measure.

Answer 24

To find the surface area, we use the same process we used in the first question, except it wants us to approximate the answer (that means it'll have decimals, __.__ instead of ___*pi) now.

A = 4 * pi * r^2
We have the fact that
r = 3.342
Plug it in to get:
A = 4 * pi * 3.342^2
A = 4 * pi * 11.169
You can multiply all of those now, since we want the approximation.

Answer 25

140

Answer 26

Yup! :)

Answer 27

21.
The volume of a sphere is 4,000 m3. What is the surface area of the sphere to the nearest square meter? (1 point)

2,614 m2
3,836 m2
1,307 m2
794 m2

Answer 28

im badd at this

Answer 29

This is another one where we'll need to solve for r. We have:
V = 4000
And we have the formulas:
A = 4 * pi * r^2
V = (4/3) * pi * r^3

Using this knowledge, we have:
4000 = (4/3) * pi * r^3
This is going to need us to use algebra again.
First, let's get rid of the 4/3 on the right side. We'll divide both sides by it.
4000 / (4/3) = (4/3)/(4/3) * pi * r^3
This simplifies down to
3000 = pi * r^3

Again, we can get rid of the pi by dividing both sides by it.
3000/pi = pi/pi * r^3
This, now, simplifies to:
954.93 = r^3

On the right hand side, we're "cubing" r, or ^3. To undo this, like we undo a "square" or ^2, we'll take a root of it. Undoing ^2 means that we take the square root. Likewise, undoing ^3 means that we take the cube root.

\[\sqrt[3]{954.93}=\sqrt[3]{r^3}\]This simplifies down to
9.847 = r
r = 9.847

Answer 30

Again, it's asking for an approximation, rounded to the nearest m^2.

Plug it in to the formula:
A = 4 * pi * r^2
A = 4 * pi * (9.847)^2
That should simplify nicely.

Answer 31

i didnt get any of the answers ugggghhh

Answer 32

i got 1217?

Answer 33

I got that too. I googled it and there's nothing wrong with my math. I don't see why that's not an answer. Try the closest one (1307), and report it to your teacher I guess.

Answer 34

i have a lot of different answers than my teacher ima post them and will u pls check them?

Answer 35

alright I guess

Answer 36

9.
What are the lateral area and the surface area of the cone shown below? Round the answers to the nearest tenth. The figure is not drawn to scale.

a cone (1 point)

LA = 615.8 ft2; SA = 1,803.3 ft2
LA = 615.8 ft2; SA = 3,166.7 ft2
LA = 1,187.5 ft2; SA = 1,803.3 ft2
LA = 1,187.5 ft2; SA = 3,166.7 ft2

Answer 37

r is 14 and h is 27 i got SA = 1952.3 and La = 1337.7

Answer 38

Those answers are both correct.

Answer 39

they arent on there ima call my teacher thank u so much

Answer 40

For questions 11 and 12, find the volume of the cylinder in terms of .
11.
a cylinder (1 point)

43.35 m3
51 m3
56.78 m3
73.695 m3

12.



h = 10 and r = 5 (1 point)

625 in.3
500 in.3
125 in.3
250 in.3

Answer 41

for 11 the r is 1.7 and the h is 15 and i got 136.19 and idk 12

Answer 42

12 i got 785

Answer 43

11 and 12 are different, they want answers in terms of pi again.
11 simplifies to 136.19, but it needs to be in terms of pi, so it's 43.35pi m^3.
12 simplifies to 785 just the same, but it needs to be in terms of pi, so it's 250pi in^3.

Answer 44

21 and 9 you should ask about though. If we're wrong, your teacher will hopefully explain the answers.

Answer 45

13.
What is the height of the cylinder? The figure is not drawn to scale.

a cylinder (1 point)

14.7 in
6.6 in
2.1 in
4.2 in
r is 7

Answer 46

v is 323.5

Answer 47

Here's the formula:
V = h*pi*r^2
I'm gonna run through the algebra:
323.5 = h*pi*(7)^2
323.5 = h*pi*49
323.5/49 = h*pi*49/49
6.6 = h*pi
6.6/pi = h*pi/pi
2.1 = h

Answer 48

thnks i got 2.1 i jus wanted to check

Answer 49

14.
What is the volume of the composite space figure to the nearest whole number? The figure is not drawn to scale.

a composite space figure (1 point)

216 cm3
90 cm3
378 cm3
306 cm3

Answer 50

Add the volumes of those two rectangular prisms (the boxy shapes).
It looks like the one on the left has the dimensions 4*9*6. The one on the right has 5*3*6.

V = (4*9*6)+(5*3*6)

Answer 51

306?

Answer 52

Yes

Answer 53

For questions 22 and 23, determine whether the two figures are similar. If so, give the similarity ratio of the smaller figure to the larger figure.

yes; 1:1.2
yes; 1:1.4
yes; 1:2.4
no

Answer 54

i cant thank u enough

Answer 55

25.
If the scale factor of two similar solids is 3:16, what is the ratio of their corresponding areas and volumes? (1 point)

3:256 and 3:4,096
27:4,096 and 9:256
6:32 and 9:48
9:256 and 27:4,096

26.
The volumes of two similar solids are 1,331 m3 and 216 m3. The surface area of the larger solid is 484 m2. What is the surface area of the smaller solid? (1 point)

864 m2
288 m2
144 m2
68 m2

Answer 56

121:1,936
1:64
4:1
1:4

25.
If the scale factor of two similar solids is 3:16, what is the ratio of their corresponding areas and volumes? (1 point)

3:256 and 3:4,096
27:4,096 and 9:256
6:32 and 9:48
9:256 and 27:4,096

26.
The volumes of two similar solids are 1,331 m3 and 216 m3. The surface area of the larger solid is 484 m2. What is the surface area of the smaller solid? (1 point)

864 m2
288 m2
144 m2
68 m2

Answer 57

24.
What is the scale factor of a cube with volume 1,331 ft.3 to a cube with volume 85,184 ft.3? (1 point)

121:1,936
1:64
4:1
1:4

Answer 58

looks like 22 is no

Answer 59

thank you

Answer 60

sorry, I have to go now

Answer 61

ok:(

Answer 62

thanks